As compared with a thin film transistor-liquid crystal display (TFT-LCD) which is the mainstream of existing display technologies, an organic light-emitting diode (OLED) display has advantages of wide viewing angle, high brightness, high contrast, low power consumption, smaller volume and lighter weight, and the like, and is the focus of attention among current flat panel display technologies.
Driving methods of organic light-emitting diode displays are classified into two types of passive matrix (PM) and active matrix (AM). As compared with passive matrix driving, active matrix driving has advantages of large amount of display information, low power consumption, long service life of a device, high contrast screen, and the like. At present, an active matrix organic light-emitting diode (AMOLED) display mainly uses a low temperature polysilicon-thin film transistor (LTPS-TFT) to drive an OLED to emit light. As shown in FIG. 1, an active matrix organic light-emitting diode display device generally includes a switching thin film transistor 2, a driving thin film transistor 1, and an organic light-emitting diode (OLED) 3. A gate of the switching thin film transistor 2 is connected to a scan line 4. A drain (or source) of the switching thin film transistor 2 is connected to a data line 5, and a source (or drain) of the switching thin film transistor 2 is connected to a gate of the driving thin film transistor 1. A source (or drain) of the driving thin film transistor 1 is connected to a power line 6, and a drain (or source) of the driving thin film transistor 1 is connected to an anode of the OLED 3. A cathode of the OLED 3 is grounded, and a storage capacitor 7 is connected between the source (or drain) and the gate of the driving thin film transistor 1. Generally, the switching thin film transistor 2 is required to have a small S factor (subthreshold swing) such that an electric current changes with a voltage greatly, whereas the driving thin film transistor 1 is required to have a large S factor such that an electric current changes with a voltage slightly. Thus, it can be ensured that the switching thin film transistor 2 has a better switching performance, which facilitates grayscale control. However, in the prior art, the switching thin film transistor 2 and the driving thin film transistor 1 are manufactured as thin film transistors having the same performance parameters, which is not helpful for effective turn-on and turn-off of the switching thin film transistor and the grayscale control.